On 2020-06-08, Maria Van Kerkhove (WHO COVID-19 technical lead) stated:
From the data we have, it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual.
We have a number of reports from countries who are doing very detailed contact tracing. They're following asymptomatic cases, they're following contacts and they're not finding secondary transmission onward. It is very rare -- and much of that is not published in the literature.
We are constantly looking at this data and we're trying to get more information from countries to truly answer this question. It still appears to be rare that an asymptomatic individual actually transmits onward.
What Van Kerkhove states above seems to contradict a recent NEJM editorial (2020-05-28):
asymptomatic persons are playing a major role in the transmission of SARS-CoV-2.
Asymptomatic transmission of SARS-CoV-2 is the Achilles’ heel of Covid-19 pandemic control
Ultimately, the rapid spread of Covid-19 across the United States and the globe, the clear evidence of SARS-CoV-2 transmission from asymptomatic persons, and the eventual need to relax current social distancing practices argue for broadened SARS-CoV-2 testing to include asymptomatic persons in prioritized settings.
Who's correct? What does the best evidence at present say?